In beseeching Iowans to boost his poll numbers in the key state, Republican Presidential candidate Donald Trump touted his strong Christian faith, which he argued has made him popular among evangelicals.

Speaking to a crowd of 2,300 at West High School in Sioux City on Tuesday during his first trip to Iowa since three state-wide polls showed his commanding lead slipping away, Trump asked, "Will you get these numbers up?"

"I promise you I will do such a good job," he continued. "First of all, I am a great Christian -- and I am -- I am. Remember that. And I do well with the evangelicals. But the evangelicals left me down a little bit this last month. I don't know what I did. But I am a great Christian.

"Please do me a favor. Let me win Iowa," he added. "Until Iowa came along, I said 'every poll' [had me in first place]. And then Iowa came -- What ... are you people doing to me?"

A recent Monmouth University poll showed Trump with 18 percent compared with retired neurosurgeon Ben Carson leading with 32 percent, while a new CBS/New York Times national poll showed twenty-six percent of Republican primary voters back Carson, giving him a four-point edge over Trump (22 percent).

"What is my competition? Do you think these guys? I'm not going to say Carson. I'm not going to say [Marco] Rubio, who really is way down. I mean I am second, that's not like terrible. I don't like being second. Second is terrible to me," Trump said. "But do you think that Ben is going to go to China?"

The billionaire businessman went on to describe his favorite Bible: one inscribed by his mother.

In the past, Trump has been praised by Christian leaders including Rev. Franklin Graham, pastor and president of Marketplace Leaders Os Hillman, and popular evangelist Jerry Falwell Jr, among others.

However, in an op-ed published in September for USA Today, columnist Kirsten Powers urged conservative evangelicals to "wake up" to the manipulations of Trump, who she argued lies about his religious beliefs to gain votes.

"Trump is a lot of things, but stupid isn't one of them," she wrote. "He clearly determined that the only way to win the Republican nomination was through an appeal to the conservative evangelical vote. Despite his multiple divorces and remarriages, longtime support for abortion rights (until recently) and prideful self-aggrandizement, Trump has emerged as the favored candidate of evangelical voters."

Citing the Presidential hopeful's lack of humility, refusal to ask for forgiveness for his sins, and failure to identify his favorite Bible verse, Powers charged that "Trump is a dangerous megalomaniac with a distorted sense of reality...Evangelical voters need to wake up."